1. Field of the Invention
The present invention relates generally to a mold assembly, and more specifically to a mold assembly having at least a resilient contact member particularly suited for the art of applying an insert-molding to a heterogeneous object.
2. Description of the Prior Art
FIG. 1 and FIG. 2 are cross-sectional views of a conventional mold assembly. A rigid mold assembly 100 is used for insert-molding a part 10 such as a heterogeneous object, wherein the material of the rigid mold assembly 100 may be metal such as aluminum, iron, steel etc. The rigid mold assembly 100 has an upper mold 110 and a lower mold 120, and an inner space 130 is formed between the upper mold 110 and the lower mold 120. The part 10 may include a non-elastic part 2 and an elastic part 4 combined with the non-elastic part 2, wherein the non-elastic part 2 may be non-polymer elastomer such as metal, ceramic, glass, plastic etc. and the materials of the elastic part 4 may be polymer elastomer such as synthetic rubbers, silicon gel etc. A method of forming the part 10 may be: disposing the non-elastic part 2 in the inner space 130, then injecting the polymer elastomer into the inner space 130 and curing the polymer elastomer, at which point the part 10 is completed.
The drawback of the above prior art method is: clearance or interference between the part 10 and the rigid mold assembly 100 occurs due to self-dimensional variation of the non-elastic part 2, deformation of the non-elastic part 2 caused by thermal expansion, or hardness of the non-elastic part 2. For example, as shown in the circular, enlarged view of FIG. 1, when the size of the non-elastic part 2 is too small, the gap 140 occurs between the non-elastic part 2 and the lower mold 120. The gap 140 will lead to overflow of the injected polymer elastomer which may be difficult to clean in post processing. As a result, the processing yield is reduced. Furthermore, as shown in the circular, enlarged view of FIG. 2, when the size of the non-elastic part 2 is too big, interference occurs between the non-elastic part 2 and the lower mold 120, thereby damaging the appearance of the non-elastic part 2. The interference between the part 10 and rigid mold assembly 100 can also occur due to thermal expansion during the insert-molding process, so that the appearance of the part 10 may be damaged.
FIG. 3 is a cross-sectional view of another conventional mold assembly. The elastic part 4 is combined on two sides of the non-elastic part 2, and the upper side A1 and the lower side A2 of the non-elastic part 2 respectively contact the upper mold 110 and the lower mold 120. Due to the lack of resilience and deformation capability of the non-elastic part 2, upper mold 110, and lower mold 120, the non-elastic part 2 is easily crushed or damaged by the upper mold 110 and the lower mold 120 when the size of the non-elastic part 2 is too big. On the other hand, as shown in FIG. 4, when the size of the non-elastic part 2 is too small, overflow of the polymer elastomer will occur after mold-locking.
Therefore, an improved mold assembly is needed, wherein a part having dimensional accuracy is formed without hurting the structure or the appearance of the part.